Resin acids toxicity

The resin acids present in pulps, particularly those from softwood, have also been found to be significantly toxic to aquatic organisms. The amount in wood varies greatly between species (Table 10.4). Between 0.3 and 3.6 kg/tonne is extracted during pulping. 

Toxicoses from pine needles have been reported in field cases, but are rare and have only occurred in pregnant cattle. No toxicity other than abortion in cattle has been demonstrated from ICA or ICA derivatives. However, the abietane-type resin acids in ponderosa pine needles (concentrated in new growth pine tips) have been shown to be toxic, but not abortifacient at high doses, when administered orally to cattle, goats, and hamsters. Pathological evaluations of intoxicated animals includes nephrosis, edema of the CNS, myonecrosis, and gastroenteritis (Stegelmeier et al., 1996). While abietane-type resin acids may contribute to the occasional toxicoses reported in the field, they do not contribute to the abortions. Most cow losses in the field are associated with difficult parturition or post abortion toxemia due to retained fetal membranes. 

A number of studies have evaluated the toxicity of pulping hquors, in particular the black liquors generated from Kraft mills. Table 8 shows a partial representation of toxicity data compiled by the NCASI (National Council of the Paper Industry for Air and Stream Improvement) and McKee and Wolf for Kraft mill pulping wastewaters [15,16]. The table indicates that hydrogen sulfide, methyl mercaptan, crude sulfate soap, and salts of fatty and resin acids are particularly... 

Hickey, C.W. Martin, M.L. Relative sensitivity of five benthic invertebrate species to reference toxicants and resin acid contaminated sediments. Environ. Toxicol. Chem. 1995, 14, 1401 -1409. 

McCarthy et al. Role of resin acids in the anaerobic toxicity of chemi-thermomechanical pulp wastewaters. Water. Res. 1990, 24, 1401-1405. 

Organic matter in unpolluted freshwater is usually in the form of humic acids (Section 13.6), which may discolor drinking water, foul ion-exchange resins, transport toxic metal ions, or generate carcinogenic chlorocarbons if the water is chlorinated (see below). Humic compounds may be removed by coagulation. Low levels of organic solutes can be removed by sorption on activated charcoal. 

Dehydroabietic acid (XIII) is the most abundant of the resin acids that occur naturally in wood and tree bark. These compounds are toxic and persistent in the environment. The effect of DOM on the photolysis of XIII was investigated at 254 nm and at X > 300 nm [74], In pure water, XI (3 mgL x) was degraded both by 254 nm radiation and simulated solar light. The degradation of XIII at 254 nm was slower in the humic surface water (Lake Sarojarvi, Finland) than in pure water. The opposite effect was observed at X > 300 nm. 

Death of the parenchyma in the sapwood of woody plants normally results in a marked increase in susceptibility of that tissue to decay. However, certain types of wounds apparently stimulate in adjacent cells the synthesis and accumulation of compounds such as lignans, stilbenes, resin acids, or tannins. The reaction zones surrounding wounds in some species show an accumulation of compounds inhibitory to decay fungi in other species the discolored wood surrounding the wounds is no more decay-resistant than the sapwood of that particular species. The ability of the sapwood to form discolored wood containing toxic components may be linked with an ability to produce heartwood resistant to decay fungi. 

Some of the advantages that can be visualized for a process of this type are a large, low-cost source of clean terpenes and resin acids improved uniformity of kraft cooking that would not be inhibited by the presence of resinous constituents no fatty or resin acid soaps that create foaming on brown stock washers and require additions of defoamers for control and, most importantly of all, no toxic fatty or resin acids in the bio-basin effluent discharge. The inherently more expensive northern wood resource, compared to subtropic plantation eucalyptus or other hardwoods, would be enhanced by the co-production of products, which would help to provide a competitive balance. 

Resin acids are toxic to fish at concentrations of 0.5-1 mg/1, but are not toxic to humans and other mammals. The toxicity of the resin acids is related to their uptake from water and accumulation in the fish [26]. The resin acids are then metabolized in the liver by formation of their glucuronic acid esters, which are excreted through the bile. The glu-curonyltransferase enzyme system in the liver can be overloaded and seriously affect the function of the liver [27]. However, resin acids, as well as fatty acids, are to a large extent removed in modern water treatment plants with mechanical and biological stages [28]. 

Other Reactants. Other reactants are used in smaller amounts to provide phenoHc resins that have specific properties, especially coatings appHcations. Aniline had been incorporated into both resoles and novolaks but this practice has been generally discontinued because of the toxicity of aromatic amines. Other materials include rosin (abietic acid), dicyclopentadiene, unsaturated oils such as tung oil and linseed oil, and polyvalent cations for cross-linking. 

The typical acid catalysts used for novolak resins are sulfuric acid, sulfonic acid, oxaUc acid, or occasionally phosphoric acid. Hydrochloric acid, although once widely used, has been abandoned because of the possible formation of toxic chloromethyl ether by-products. The type of acid catalyst used and reaction conditions affect resin stmcture and properties. For example, oxaUc acid, used for resins chosen for electrical appHcations, decomposes into volatile by-products at elevated processing temperatures. OxaUc acid-cataly2ed novolaks contain small amounts (1—2% of the original formaldehyde) of ben2odioxanes formed by the cycli2ation and dehydration of the ben2yl alcohol hemiformal intermediates. 

Esters represent an important class of chemical compounds with applications as solvents, plasticizers, flavors and fragrances, pesticides, medicinals, surfactants, chemical intermediates, and monomers for resins. Recently, esters of amino acids have attracted attention regarding their use as biobased surfactants with excellent adsorption and aggregation properties, low toxicity, and broad biological activity. 

Arsenic compounds can be very effective corrosion inhibitors but their toxicity, ineffectiveness in hydrochloric acids above 17% active and in the presence of H S, and their ability to poison refinery catalysts has limited their use (148). Epoxy resins have been coated onto metal surfaces and cured with a polyamine to reduce corrosion (149). 

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